Fluid fuel burner control system



Jan. 14 1941. H. T. SPARROW 2,228,997

FLUID FUEL BURNER CONTROL SYSTEM Filed Feb. 16, 1959 (02 [Cl 6 a a 7 1: 89

\ QVERLAFPING IN ON DIRECTION ONLY 59 |25 12 OVERLAPPING 1, [01

inventor Huber T. Sparrow I plg'zv M Patented Jan. 14, 1941 UNITED STATES PATENT 7?" 2,228,997 FLUID FUEL BURNER CONTROL SYSTEM Application February 16, 1939, Serial No. 256,689

14 Claims.

The present invention is concerned with a fluid fuel burner control system and more particularly with such a system in which means is provided for checking the ignition spark.

In Patent No. 2,143,076 issued to Allan M. Koerner, on January 10, 1939, a fluid fuel burner control system is disclosed in which means is provided for checking the ignition spark. This means takes the form of a pair of auxiliary windings on the ignition transformer, each of which controls a separate relay. When the spark is proper, both of the relays will be energized but when there is either a short circuit condition or an open circuit condition in the ignition circuit; one or the other of the two relays is not energized so that the fuel feeding means is not placed in operation. Such a system has an advantage over many types of previous systems in that it checks for both a short circuit and an open circuit condition. The system has the disadvantage that it is responsive only to the current flow in the ignition circuit and that if this current flow is caused by a condition simulating a spark in the leads between the secondary winding and the spark electrodes, 2. false indication of a proper spark may be given. t

In the copending application of Willis H. Gille, Serial No. 94,502, filed August 6, 1936, a spark checking system is disclosed in which a thermocouple is closely associated with the spark gap.

This thermo-couple is heated only when there is a proper spark directly at the spark gap since in the event of either a short circuit or an open circuit condition, very little heat is generated at the spark gap. This system has the disadvantage that the thermo-couple inherently is slightly slow in response. While a thermo-couple is much quicker in response than other temperature responsive means in that it depends merely upon the difference in temperature between two points rather than upon the absolute temperature, there is nevertheless an appreciable delay in the response of the thermo-couple to the termination of ignition.

The present invention is concerned with a sys tem wherein the advantageous features of both of the aforementioned systenis'are combined in a novel manner to provide a spark checking system having new and unexpected advantages.

An object of the present invention is to provide a fluid fuel burner control system having a means directly but slowly responsive to the temperature of the ignition spark gap, a second means quickly responsive to the current flow in the ignition circuit, and means for causing a flow of fuel to the burner only in the event ofboth means indicating the presence of a proper spark.

A further object of the invention is to provide such a system wherein the slow acting means is a thermo-couple.

A further object of the invention is to provide such a system in which the slow acting means is an element having a negative temperature coefiicient of resistance.

A further object of the present invention is to provide such a system wherein the ignition cannot initially be energized until the slow actin temperature responsive checking means is in its cold position.

A still furtherobject of the present invention is to provide such a system in which the initial energization of the ignition means is dependent upon both spark checking means being in their deenergized positions.

A further object of the present invention is to provide a novel spark checking system employing an element having a negative temperature coefificient of resistance responsive to the tempera-= ture at the spark gap.

A still further object of the present invention is to provide a new and novel circuit of the type employing auxiliary windings on the ignition transformer for checking the presence of a proper spark. j A further object of the invention is to provide a fluid fuel burner control system having a timing switch for shutting down the system unless burner operation occurs within a predetermined period of time and in which there is a spark checking system with means to insure that the timing period of the timing switch does not be-- gin until after the spark checking system has indicated the establishment of a proper spark.

Other objects of the invention be apparent from a consideration of the accompanying specificat'ion, claims and drawing of which:

Figure 1 is a schematic view of one form of the invention, and

Figure 2 is a view of a portion of the system shown in modified form.

Referring to the drawing, a, fluid fuel burner is generally designated by the reference numeral In. This burner comprises a. nozzle I l with which is associated a motor l-2 through which fuel is forced by a blower driven by a motor I 2.

Located adjacent to the open end of the burner nozzle H is a pair of spark electrodes l4 and I5. These two electrodes l4 and I5 are subjected to a voltage produced by an ignition transformer 16. This transformer is shown as being of the 1 gization of relay coil 6|.

leakage type comprising a magnetic core i! having two side legs l8 and i9, two end cross legs 28 and 2|, and an intermediate cross leg 22 which has a gap 23 therein and which functions as a leakage path. The primary winding 25 is located upon the cross leg 20 and a secondary winding 26 on the cross leg 2|. Oneterminal or the secondary winding 26 is connected by means of a conductor 28 to the electrode E4. The other terminal is connected by means of conductors 29 and 30 to the electrode l5. This latter terminal of the secondary 26 is connected by means of conductors 29 and 3| to ground at 32.

Electrode l5 takesthe form of a thermo-couple in the species of Figure 1. This thermocouple comprises the usual two elements 33 and 34 of dissimilar thermo-lectric characteristics. The two elements are Joined at 35 to provide a hot junction. It will be noted that this hot junction is immediately adjacent the gap between the two electrodes. The thermo-couple [5 controls the energization of a relay 98 which includes a relay coil 31 and two switch blades. 39 and 40 which are biased to the right. Switch blade" 40 engages a fixed contact 4i when relay coil .31 is deenergized and switch blade 39 is adapted to be moved into engagement with a fixed contact 42 when relay coil 31 is energized. It is to be understood that the thermo-couple is of relatively high efficlency and that the various conductors between the thermo-couple and its associated relay coil are of relatively large size so that the small electromotive. force generated by the thermo-couple produces sufficient current flow through the relay coil 38 to cause the same to pull in its associated switch blades. Such thermo-couple actuated relays "are now well known in the art.

Located on the side leg i8 is an auxiliary secondary winding 44 which is connected to a relay coil 45 ofa relay 46. The relay 48 comprises a switch blade 41 which is adapted to be moved into engagement witha fixed contact 48. The switch blade 41 is normally biased out of engagement with the contact 48.

Located upon the leakage leg 22 is a second auxiliary secondary winding 49. This winding 49 is adapted to controlthe energization oi" a relay 50 comprising a relay coil 58, switch blades 52, 53, and 54 and associated contacts 55, 56, and 51. The switch blades 52, 53, and 54 are biased out of engagement with contacts 55, 56, and 57 and are adapted to be moved into engagement therewith upon the energization of relay coil 5!.

In addition to relays 38, 46, and 50 there are two other relays in the system, these being designated by the reference numerals 59 and 59. The relay 58 comprises a relay coil 6| with which are associated switch blades 62, 63, and G4. The three switch blades 62, 63, and 64 are adapted to engage contacts 85, 66, and 61, respectively. The switch blades are normally biased'out of engagement with the contacts and are adapted to be moved into engagement therewith upon ener- The relay 59 comprises a relay coil 69, switch blades 10 and H and fixed contacts l2, i3, and 14. Switch blades 10 and M are biased into engagement with contacts 53 and I4 and are adapted to be moved out of engagement therewith upon energization of relay coil 69. Upon such energization of relay coil 69, the switch blade 10 is moved into engagement with contact 72 before it is moved out of engagement with contact l3. In

other words, the switch blade 'Hl overlaps the contacts 12 and 13.

The energization of relay coil 58, which constitutes the main controlling relay of the system, is controlled by a room thermostat 16. This ther mostat comprises a bimetallic element 11 to which is secured a composite contact arm 78 which is adapted to sequentially engage fixed contacts l9 and 80. The bimetallic element I1 is so arranged that upon a temperature fall the con tact arm 18 is adapted to engage first contact 19 and then contact 80. The portion of the contact arm which engages contact 19 is flexible to permit such further movement of the contact arm. Associated with the bimetallic element is a heater 8| which is adapted to locally heat the bimetallic element to cause the thermostat to cease calling for heat slightly before it would solely by reason of the rise in ambient temperature.

A thermal safety switch is generally designated by the reference numeral 85. This switch is preferably of the type shown in the patent to Frederick S. Denison No. 1,958,081 of May 8, 1934. This switch, as shown for purposes of illustration, comprises a pair of switch blades 86 and 81, the switch blade 81 being biased downwardly away from switch blade 86 but being normally held in engagement therewith by a bimetallic element 88 with which is associated an electrical heater 89. Upon heating of the bimetallic element 88, the element is adapted to slowly move toward the right. If such movement continues sufiiciently far, switch blade 9'! will be allowed to separate from switch blade 96. After the switch blades 86 and 8'! have once been separated, it is necessary to manually reclose the switch.

A stack switch is generally designated by the reference numeral 99. prises a bimetallic element (not shown) which is connected to a switch blade 9i through a slip friction connection. The switch blade 9| is adapted to be moved between contacts 92 and 93. Contact 92 is engaged when the temperature is falling or is cold while the contact 93 is engaged upon a rise in temperature. The contact structure is so arranged that engagement of switch blade 9| with contact 93 is effected before switch blade 9! has disengaged contact 92. Upon a tem- Operation The various elements are shown in the position they occupy when the thermostat i6 is satisfied, that is, when the temperature to which it is sub.. jected is at or above the desired temperature. Let it be assumed now that the temperature drops until both contacts 19 and 80 are engaged by contact arm 18. Until both contacts are engaged, no circuit is established. Upon such engagement, however, the following circuit is established to relay coil SI of relay 58: from the upper terminal of secondary 96, through conductor l0i, switch blades 81 and 86, conductor Hi2, contact 19, contact arm 18, contact 80, conductors H03 and I04, contact 4!, switch blade 49, conductors 805, I86,

and I01, contact 14, switch blade II, conductors I09 and H0, contact 92, switch blade 9|, conductor III, relay coil 6|, and conductor II2 to the other terminal of secondary winding 96,

The energization of relay coil 6| as a result of the establishment of the above traced circuit results in switch blades 62, 63, and 64 being moved into engagement with contacts 65, 66, and 61. The engagement of switch blade 63 with contact 66 establishes a circuit to relay coil 6| which is independent of the engagement of thermocouple switch blade 40 with contact 4|, this circuit being as follows: from the upper terminal of secondary 96 through conductor IOI, switch blades 81 and 86, conductor I02, contact I9, contact arm I8, contact 80, conductors I03 and H4, contact 66, switch blade 63, conductors II5, H6, and I01, contact I4, switch blade II, conductors I09 and H0, contact 92, switch blade 9|, conductor III, relay coil 6|, and conductor 2 to the other terminal of secondary 96. It will be noted that the original energizing circuit to the relay coil depended upon the thermo-couple relay 38 being deenergized so that the switch blade was in engagement with contact 4|. This was to insure that the system would not be started when the thermo-couple was still hot from a previous operation so as to give a false check.

At the same time as the circuit just traced to relay coil 6| is established, a further maintaining circuit is also established to relay coil 6| as follows: from the upper terminal of secondary 96 through conductor IOI, switch blades 81 and 86, conductor I02, contact I9, contact arm I8, bimetallic element 11, conductor I I8, heating element 8|, conductor 9, contact 61, switch blade 64, conductors H6 and I'I, contact 14, switch blade II, conductors I09 and H0, contact 92, switch blade 9|, conductor III, relay coil 6|, and conductor 2 to the other terminal of secondary 96. It will be noted that this new circuit is independent of the engagement of contact I8 with contact 80 so that the circuit to relay coil 6| is not interrupted until contact arm I8 has separated from contact 80. This is for the purpose of providing a differential between starting and stopping of the apparatus so as to prevent an excessive number of operations and also to prevent chattering of the relay when the thermostat first makes or breaks its contacts. It will also be noted that in the circuit last traced, the heater 8| was connected. The heater 8| is, however, relatively deenergized as long as contact arm I8 engages contact 80 inasmuch as the same is effectively shorted out by a circuit from heater 8| through conductor II8, bimetal I1, through contact arm I8, contact 80, conductors I03 and H4, contact 66, switch blade 63, conductor II5, switch blade 64, contact 67 and conductor 9 to heater 8|.

The engagement of switch blade 62 with contact 65 results in an energizing circuit being established to the primary winding 25 of the ignition transformer I6 as follows: from line wire 99 through conductor |2|, contact 65, switch blade 62, conductors I22, I23, and I24, primary winding 25 and conductor I26 to the other line wire 98. Upon the energization of the primary winding 25, a spark will normally be produced between the electrode I4 and the thermo-couple electrode I5. The spark between electrodes I4 and I will cause a gradual heating of the hot junction 35 of thermo-couple I5. The thermocouple I5 is connected to relay coil 38 by an energizing circuit as follows: from .thermo-couple I5 through conductors 30 and 3|, through the ground," relay coil 3'1, and conductor I28 to the other terminal of the thermo-couple. When the hot junction becomes sufliciently heated, the energizing current flowing to relay coil 31 through this circuit will be sufficient to cause switch blade 40"to be moved out of engagement with contact 4| and switch blade 39 into engagement with contact 42.

As soon as switch blade 39 moves into engagement with contact 42, an energizing circuit is established to relay coil 45 as follows: from the auxiliary winding 44 through conductors I29 and 3| to ground, through the ground, conductor I30, switch blade 39, contact 42, conductor I3I, relay coil 45, and conductor I32 to the other terminal of auxiliary winding 44. The auxiliary winding 44 will be energized so long as the resistance of the spark gap circuit is not excessively low. In other words, the winding 44 is energized by the same flux as the winding 26. If the resistance of the secondary circuit is excessively low, very little flux will flow through the portion including secondary 26, the larger portion of the flux flowing through the leakage leg 22. The result will be that the flux to which winding 44 is subjected will be insuflicient to energize relay coil 45. If the resistance of the circuit is not excessively low, however, relay coil 45 will be energized to cause engagement of switch blade 47 with contact 48.

Upon switch blade 41 engaging with contact 48, a circuit is established to the relay coil 5| of relay 50 as follows: from the upper terminal of winding 49 through conductor I34, switch blade 41, contact 48, conductor I35, relay coil 5|, conductor I36 through the ground, and conductor I3'I to the other terminal of winding 49. The auxiliary winding 49 is energized sufliciently to cause relay coil 5| to actuate its associated switch blades only if the resistance in the secondary circuit is not excessively high. If an open circuit condition exists in the secondary circuit or if the resistance is extremely high so that a spark would not occur, the flux will all pass through the leg of the transformer upon which the secondary winding 26 is located so that practically no flux will pass through the leakage leg. Under these circumstances, of course, winding 49 will be incapable of energizing relay coil 5| sufliciently to actuate the relay. If, however, the current flow in the secondary winding is of a value accompanying a proper spark, the relay coil 5| would be energized to cause switch blades 52, 53, and 54 to move into engagement with contacts 55, 56, and 51.

The thoroughness of the spark checking operation is increased by reason of the fact that the circuit between auxiliary winding 49 and its relay coil is the last of the spark checking circuits to be closed. As soon as this circuit is closed, current flows in winding 49 so as to cause counter flux in the leakage leg and thus force more of the flux through the portion of the core on which windings 26 and 44 are located. Since winding 49 and relay 46 are provided for checking against a condition in which insuflicient flux flows through the leakage leg, this diversion of some of the flux from the leakage leg makes this test more rigid. Moreover, since tests have already been made to insure that the spark is adequate and since the forcing of more flux through the secondary portion of the core increases the intensity of the spark, it will be assured that the spark is even more intense than absolutely necessary. This precludes any possibility of the spark being blown out when the burner is started due to the spark being just suflicient to cause the spark checking arrangement to function but insuflicient to withstand the draft created by the burner blower.

Upon switch blade 54 engaging contact 51, a new relay energizing circuit is established through the heater element 89. Inasmuch as any circuit through contact 88- parallels between contact 88 and switch blade M, an equivalent circuit through the heater 86, the only circuit which will be traced is that through heater 8!] this circuit being as follows: from the upper terminal of secondary 98 through conductor |8|, switch blades 81 and 86, conductor H82,

contact I9, contact arm "l8, bimetallic element 11, conductor 8, heater 8i, conductor M9, contact 61, switch blade 64, conductors H6, 196, and I3'I,switch blade 54 contact 51, iconductor I38, heating element 89, conductors I39 and H8, contact 92, switch blade 9|, conductor I I I, relay coil 8|, and conductor I I2 to the other terminal ofsecondary 98. It will be noted that the circuit just traced is through heating element 89. The heating element 89 is not immediately energized, however, since there still exists the previously traced circuit through switch blade 'II and contact I4 which parallels the heating element 89.

Engagement of switch blade 52 with contact 55 results in an energizing circuit to relay coil 69 as follows: from the line wire 99 through conductor I2 ,I,' contact 65, switch blade 62, conductors I22 and 0, switch blade 52, contact 55, conductors Ill'and .I42, contact 13, switch blade 10, conductor 3, relay coil 89, and conductor I to the other line wire 98. The energization of relay coil 89 causes switch blade III to move 'fromengagement with contact 18 into engagement with contact 12. As previously noted, the engagement of switch blade III with contact 12 is effected before the disengagement of the switch blade from contact I3. Upon switch blade 10 engaging contact 12, a, holding circuit is established to relay coil 89 as follows: from line wire 99 through conductor I 2|, egigtact 65, switch blade 82, conductors 22 and relay coil 69, and conductor 4 to the other line wire 98. The new energizing circuit Ior relay coil 69 is dependent only upon the en ergization of relay 58 and is independent of relay 59.

The energization of relay coil 69 also causes switch blade III to disengage from contact M. This interrupts the first traced circuits to relay coil 8| so that the only circuits remaining to this coil are through heating element 89.

The closure of switch blade 52 with,contact 55 also results in a circuit being established to the oil burner motor 62 as follows: from line wire 99 through conductor H20, contact 85. switch blade 62, conductors I22 and M8, switch blade 52, contact 55, conductors Mill and 8, oil burner motor I2, and conductor Hill to line wire 98.

It will be noted from the preceding description that upon relay 50 becoming energized the oil burner is started and that relay 59 is enersized to break the shunt circuits around the heating element 89 and to cause this element to be energized. The energization of heating element 89 results in the timing operation of the thermal switch 85 being initiated. Thus with the present system, this timing operation is not contact 12, switch blade I8, conductor I48,

initiated until a check has been established on the ignition spark. This is a particularly valuable feature in a system employing a thermocouple as a spark checking means since a thermo-couple inherently requires a certain 6 amount of time to respond to the presence of a spark. This time may be somewhat variable and thus results in a variation in the timin period for ignition of the burner after the oil has once been supplied, if the timing period is 10 allowed to begin with a call for heat as has been previously the case. Even in a system in\ which there is a quick acting spark check, it may so happen that the ignition apparatus 'does not immediately respond and first produces a proper l5 spark only at the end of the normal timing period. This will result in the apparatus shutting down by reason of the release of the thermal safety switch even though conditions are at that moment proper to establish combustion. 20

With the present system, the time for establishing ignition and the checking thereof may be I as long as possible without affecting the timing period for the ignition of the fuel.

Inasmuch as the ignition has been checked be- 25 fore the oil burner is turned on, combustion will presumably take place immediately. This will eventually cause a rise in stack temperature-causing the stack switch blade 9| to first engage contact 98 and then disengage contact 92. The en- 80 gagement of switch blade 9| with contact 99 will result in the following energizing circuit being established to relay coil 6| through the hot contact 93: from the upper terminal of secondary 98 through conductor |8|, switch-blades 81 and 85 86, conductor I02, contact I9, contact arm 18, bimetal 11, conductor 8, heating element 8|, conductor 9, contact 51, switch blade 64, conductors ||9,,|||5, and I31, switch blade 54, contact 51, conductor I49, switch blade 53, contact 55,

heating element 89 is completely interrupted. 59

Under normal circumstances this movement in the position of stack switch blade 9| will occur before heating element 89 has heated bimetal 88 to a point to effect opening of switch blades 81 and 88. If, however, the establishment of com- .55

bustion requires an excessive period of time, the switch blades 81 and 86 are separated so as'to interrupt all circuits to relay coil 6| and thus deenergize the entire system.

Under normal circumstances, the operation of 5 the burner will be established within the proper time and will cause the temperature of the space in which thermostat 18 is located to gradually raise contact arm 18 and separate it from contact 88. When this takes place the only circuit remaining to relay coil 6| is the one including the heating element 8|. Up until this time, the heating element 8| has been shunted by a circuit previously traced. When all of the current torelay coil 8| begins to flow through heating element 9| this heating element rises in temperature and subjects the bimetal I1 to-a temperature higher than ambient. The effect of this is to cause the movement of contact arm 18 to the right to be accelerated so as to cause contact arm I8 to separate from contact arm I9 in a much shorter period of time than if separation were caused solely by a rise in ambient temperature. It will be noted that the heat is not applied to the thermostat, however, until the ambient temperature had risen sufficiently to cause contact arm I8 to separate from contact 80. The application of heat from heater BI is thus used to accelerate an already existing movement of contact arm '18. The purpose of this, as is well known in the art, is to anticipate the delivery of heat to the space and thus prevent overshooting of the temperature due to the lag in delivery of the heat.

The system shown is of the constant ignition type. With this system, it is highly desirable to insure even after the oil burner is running that the ignition remains established at all times. The present system insures that upon failure of ignition, the oil burner is stopped and ignition is not reestablished until time has been provided for elimination of accumulated unburned oil vapor from the furnace. Let it be assumed that either a short circuit or an open circuit condi tion occurs in the ignition circuit. Either of these conditions will result in the deenergization of relay coil 51 with the resultant separation of switch blades 52, 53, and 54 from their associated contacts 55, 56, and 51. The separation of switch blade 54 from contact 51 will interrupt the energizing circuit of relay coil BI since the only energizing circuits to relay coil 6| traced in the foregoing portion of the specification which are not through switch blade 54 and contact 51, are through contact I4 and switch blade I I. Switch blade II is engaged with contact 14, however, only when relay coil 69 is deenergized. Since relay coil 69 has a holding circuit through switch blade 62 and contact 65, it is not deenergized until after relay 58 is deenergized. Thus upon relay 50 being deenergized, with the resultant separation of switch blade 54 from contact 51, relay 58 is deenergized. Upon thisrelay being deenergized, the operation of the entire system is terminated. The system cannot again be restarted until stack switch has cooled down to a value such that switch blade 9| has reengaged contact 92 and until the thermo-couple l5 has cooled down sufiiciently to permit relay 38 to move to its deenergized position. This is true because the initial energizing circuit for relay coil 8| is through both contact 92 of the stack switch and the out contact M of the relay 38. Thus even though there be no stack switch present, a delay is interposed between the interruption of ignition and the reestablishment thereof, this delay arising because of the time ra uired forthe cooling of the thermo-couple. Thus the system can be successfully operated without a stack switch by merely connecting conductors H0 and I50 directly to conductor I II and by eliminating the thermal safety switch.

Such a delay will also result whenever the system is energized, even momentarily, for any reason whatsoever. Thus if there is a momentary power failure or if the thermostat is manually opened and then closed, it is impossible to reenergize the ignition until sufficient time has elapsed for any unburned gases to pass up the stack.

It will be seen that I have provided an extremely safe fluid fuel burner control system in which a spark is checked in a manner as to absolutely preclude the possibility of a faulty check and in which assurance is had that the oil burner will be given its normal timing period in which to be placed in operation despite any delay that may occur in connection with the establishment 01' or the checking of ignition.

While the electrode l5 has been shown in Figure 1 as being formed of a thermo-couple, it is possible to employ in lieu thereof an arrangement utilizing a ceramic element I60 having a negative temperature coeflicient of resistance. This element is connected into the circuit in a very similar manner to the Way in which thermocouple I5 was connected in Figure 1. In other words, one terminal of the element is connected to the conductor 30 which is connected through I conductor 29 to one winding of the secondary 25. The conductor 30 is also connected to ground through conductor 3 I The other terminal of the element I60 is connected through the conductor I28 to the relay coil 31 of relay 38. With the use I j is accomplished by the provision of an extra secondary winding IBI which may be provided on the transformer 95. The right hand terminal of relay coil 31 is connected through conductor I62 to the secondary winding I6I and the other terminal of the secondary winding is connected to ground at I63. Upon the existence of a proper spark, the ceramic element I60 will be heated to cause a fiow of current through relay coil 31 suflicient to move the associated switches to their energized position. The ceramic element thus works in essentially the same manner as the thermo-couple, one principal difference being that the operation of the ceramic element depends solely upon the temperature to which it is subjected and not the difference in the temperature between two points therof as in the case of the thermo-coup-le. The ceramic element on the other hand, causes a much more abrupt change in current delivered to the relay and hence minimizes relay chattering.

While-I have shown certain specific embodiments of the invention for purposes of illustration, it is to be understood that the invention is limited only by the scope of the appended claims.

Iclaim as my invention:

1. In combination, a fluid fuel burner, ignition means comprising a high tension ignition circuit including a spark gap, means directly but slowly responsive to the temperature at the spark gap, means quickly responsive to the current flow in said ignition circuit, and means for causing fuel to be fed to said burner only when said temperature responsive means and said current responsive means both indicate the presence of a proper spark.

2. In combination, 'a fluid fuel burner, ignition means comprising a high tension ignition circuit including a. spark gap, first spark checking means including a device directly but slowly responsive to the temperature at the spark gap and movable between cold and hot positions, second spark checking means quickly responsive to the current flow in said ignition circuit, means for initiating energization of said ignition means only when said first checking means is in its cold position, and means for causing fuel to be fed to said burner only when said first checking means is in its hot position and said second checking means indicates the presence of a current in said ignition circuit of a magnitude accompanying a proper spark.

3. In combination, a fluid fuel burner, ignition means comprising a high tension ignition circuit including a spark gap, a thermo-couple having its hot junction adjacent said spark gap, a controller associated with said thermo-couple and movable between cold and hot positions depending upon the output of said thermo-co uple, means quickly responsive to the current flow in said ignition circuit, and means for causing fuel to be supplied to said burner only when said controller is in its hot position and said current responsive means indicates the presence of a proper spark.

4. In combination, a fluid fuel burner, ignition means comprising a high tension ignition circuit including a spark gap, a thermo-couple having its hot junction adjacent said spark gap, a controller associated with said thermo-couple and movable between cold and hot positions depending upon the output of said thermo-couple, means quickly responsive to the current flow in said ignition circuit, means for initiating energization of said ignition means only when said controller is in its cold position, and means for causing fuel to be fed to said burner only when said controller is in its hot position and said current responsive means indicates the presence of a proper spark.

5. In a fluid fuel combustioncontrol system; electrically operated fuel feeding means; a high voltage circuit including a spark gap for igniting the fuel; a transformer including a core, a primary winding, and a secondary winding connected in said high voltage circuit; an energizing circuit for said fuel feeding means including switch means controlling said circuit; and electromaghetic actuating means for said switch means; a temperature responsive device adjacent said spark gap; means secured on said transformer core and directly responsive to the flux flow therein; and means including both said temperature responsive device and said flux responsive means operative to cause said electromagnetic actuating means to close said switch means only when said temperature responsive device is subjected to the heat of a proper spark and when the flux assumes a value within the range accompanying a proper spark.

6. In a fluid fuel combustion control system; electrically operated fuel feeding means; a high voltage circuit including a spark gap for igniting the fuel; a transformerincludin'g a core, a primary winding, and a secondary winding connected in said high voltage circuit; an energizing circuit for said fuel feeding means including switch means controlling said circuit; an electromagnetic actuating means for said switch means; a thermo-couple having its hot junction adjacent said spark gap; means secured on said transformer core and directly responsive to the flux flow therein; and means including both said thermo-couple and said flux responsive means operative to cause said electromagnetic actuating means to close said switch means only when the hot junction of said thermo-couple is subjected to the heat of a proper spark and when the flux amumes a value within the range accompanying a proper spark.

'7. In a fluid fuel combustion control system; electrically operated fuel feeding means; a high voltage circuit including a spark gap for igniting the fuel; a transformer including a core, a

primary winding, and a secondary winding connected in said high voltage circuit; an energizing circuit for said fuel feeding means including switch means controlling said circuit; an electromagnetic actuating means for said switch means;

1 a resistance element having a negative temperature coefficient of resistance located adjacent said spark gap; means secured on said transformer core and directly responsive to the flux flow therein; and means including both said resistance element and said flux responsive means operative to cause said electromagnetic actuating means to close said switch means only when said resistance element is subjected to the heat of a proper spark and when the flux assumes a value within the range accompanying a proper spark.

8. In combination; a fluid fuel burner; means for controlling the flow of fuel to said burner; means for igniting the fuel, said igniting means comprising a high voltage source of power and a pair of spaced terminals each connected to said source of power, one of said terminals including. a resistance element having a negative temperature coefficient of resistance; an electrical circuit including said resistance element, a source of power, and current responsive means; and means controlled by said current responsive means and operable to cause a flow of fuel to said burner only when said resistance element is subjected to the heat of a normal spark.

9. In a fluid fuel burner control system, a fluid fuel burner, electrically operated means for controlling the flow of fuel to said burner and operable upon energization thereof to admit fuel to the burner, meansfor igniting the fuel, said igniting means comprising a high voltage source of power and a pair of spaced terminals each connected to said source of power, one of said terminals including a -resistance element having a negative temperature coefficient of resistance and extending adjacent to the gap between said terminals, a switch in the circuit of said fuel controlling means, and electromagnetic actuating means connected to a source of power in series switch in the circuit-of said fuel controlling means, and electromagnetic actuating means connected to a source of power in series with said resistance element.

11. In a fluid fuel combustion control system; fuel feeding means; ignition means comprising a high voltage circuit having a spark gap for igniting the fuel; a leakage transformer comprising a core, a primary winding, and a'secondary winding connected in said high voltage circuit, said core having a portion constituting a leakage path around that portion of the core on which the secondary winding is located; and means respontive to a condition of said ignition means and operative upon said condition assuming a value accompanying a proper spark to force part of the flux in the leakage path portion of the transformer into the secondary portion to increase the voltage in said high voltage circuit and thereafter to cause said fuel feeding means to deliver fuel to said burner.

12. In a fluid fuel combustion control system; fuel feeding means; ignition means comprising a high voltage circuit having a spark gap for igniting the fuel; a leakage transformer comprising a core having a leakage leg, at primary winding on one side of said leakage leg, a secondary winding on the other side of said leakage leg, and an auxiliary winding on the leakage leg itself; a normally open low impedance circuit including said auxiliary winding; and means responsive to a condition of said ignition means and operative upon said condition assuming a value accompanying a proper spark to close said 10w impedance' circuit and thereby force part of the flux normally in the leakage leg of the transformer core into the secondary portion to increase the voltage in said high voltage circuit and there-' after to cause said fuel feeding means todeliver fuel to said burner.

13. In a fluid fuel combustion control system; electrically operated fuel feeding means; ignition means comprising a high voltage circuit having a spark g ap for igniting the fuel; a leakage transformer comprising a core having a leakage leg, a primary winding on one side of said leakage leg, a secondary winding on the other side of said leakageleg, and an auxiliary winding on the leakage leg itself; a relay comprising a normally open switch and a low impedance relay coil for closing said switch, said switch controlling the energization of said fuel feeding means and said relay coil being connected to said auxiliary winding; a normally open second switch in the connections between said auxiliary winding and said relay coil; and means responsive to one condition of said ignition means and operative upon said condition assuming a value accompanying a proper spark to close said second switch and thereby force part of the flux normally in the leakage leg of the transformer core into the secondary portion to increase the voltage in said high voltage circuit, said auxiliary winding being effective if the flux in the leakage leg is still of a value accompanying a proper spark to energize said relay and thereby cause the energization of said fuel feeding means.

14. In a fluid fuel combustion control system; electrically operated fuel feeding means; ignition means comprising a high voltage circuit having a spark gap for igniting the fuel; a leakage transformer comprising a core having a leakage leg, a primary winding on one side of said leakage leg, a secondary winding and a first auxiliary winding on the other side of said leakage leg, and a second auxiliary winding on the leakage leg itself; a relay comprising a normally open switch and a low impedance relay coil for closing said switch, said switch controlling the energization of said fuel feeding means and said relay coil being adapted to be connected in a closed circuit with said second auxiliary winding, the impedance of said relay coil being sufficiently low that when said second auxiliary winding is connected in a closed circuit therewith, part of the flux normally in the leakage leg of the transformer is forced into the secondary portion to increase the voltage in said high voltage circuit; and a second relay comprising a relay coil connected to said first auxiliary winding and a switch controlling the connections of said second auxiliary winding to the relay coil of said first mentioned relay.

HU'BERT T. SPARROW. 

